Various gaseous-propellant gun systems for launching a projectile have been developed in the past. For example, U.S. Pat. No. 2,129,875 to Rost discloses a firearm for propelling a projectile. The firearm is generally comprised of a single-acting piston, a compression chamber, a barrel with a bore for receiving and launching a projectile and a gasoline injection apparatus. Upon advancement of the piston toward the barrel bore and ignition of the compressed fuel-air admixture, the projectile is launched. To assist and enhance the propulsion of the projectile from the firearm, the projectile is provided with a solid composition of potassium chlorate that serves as an oxidant in enabling faster burning of and greater thrust generation by the admixture. U.S. Pat. No. 3,496,827 to Dardick concerns a repetitively operable double-breech gun system. The system is generally made up of a primary breech for receiving a conventionally fired piston and a secondary breech for receiving and releasably holding the projectile to be launched. A compressible gaseous propellant chamber is interposed between the breeches. Upon firing of the piston, the gaseous medium in the chamber, such as helium or hydrogen is compressed, thereby launching the projectile. U.S. Pat. No. 3,712,171 to Sweigart concerns a liquid-propellant gun system. The system is provided with a liquid propellant receiving chamber and a combustion chamber. A normally-closed gate valve and a spring-biased piston separate the chambers. Upon admission of the propellant into the propellant chamber, the piston is advanced in one direction against the action of its spring bias towards the combustion chamber. Opening the valve forces the propellant into the combustion chamber for causing launching of the projectile as the result of the spring urging the piston in the opposite direction. U.S. Pat. No. 4,047,465 to Wohlford concerns a gun system for launching a projectile. The system is generally made up of a solid-propellant filled chamber, a lightweight gaseous medium filled chamber and a liner for separating the chambers. Upon ignition of the propellant, the liner advances in more than one direction to progressively collapse the gaseous medium chamber thereby compressing the gaseous medium therein so as to cause launching of the projectile. U.S. Pat. No. 4,038,903 to Wohlford relates to a gun system of telescopic construction for launching a projectile. The system is generally made up of a piston-barrel subassembly and a closed end cylinder for slidably receiving the barrel piston subassembly between its ends. A solid propellant is disposed at one end of the cylinder and a lightweight gaseous medium at the other end. A fracturable pin is connected to a projectile so as to prevent accidental launch of the projectile from the barrel of the subassembly until the gaseous medium is sufficiently compressed after ignition of the propellant during system use. However, none of the aforediscussed references, whether taken alone or in any combination, remotely suggest an improved gaseous-propellant gun system for launching one or more projectiles. The system has, among other things, a housing that is provided with an internal combustion chamber at one end, and a lightweight gaseous medium chamber at the opposite end. A projectile receiving barrel is connected to the housing. A double-acting piston is slidably mounted in the chambers for reciprocal advancement between the ends of the housing. A projectile support and handling arrangement functions to position the projectile in the barrel bore. Upon advancement of the piston means, the gaseous medium is compressed and causes launching of the projectile when the projectile is separated from the projectile support and handling arrangement.